1. Technical Field
The present invention relates to data processing systems and, in particular, to automated tape cartridge loading/unloading systems. Still more particularly, the present invention relates to an automated tape cartridge loading/unloading system which includes a method and system for providing a hard stop in a loader having a movable loader tray for a robot in the system.
2. Description of the Related Art:
There is a need in data processing systems to provide for permanent storage of large quantities of data utilized by the systems. Typically, tape drives included within these systems are utilized to store this data on magnetic tapes. In order for a computer within the system to access data stored on a tape, the magnetic tape must first be loaded into the tape drive. Very often, multiple tapes may need to be accessed by a data processing system in order to utilize the data stored on these tapes. Therefore, multiple tapes may need to be loaded into and unloaded from the tape drive during a relatively short period of time.
In some data processing systems, many tape drives may be concurrently coupled to the system. In these systems, it can be very time consuming for a user to repeatedly load and unload cartridges from the various tape drives. Therefore, often a robot will be utilized to perform the loading and unloading operations. The robot will typically include a gripper which is attached to an arm of the robot to grip, or hold, a tape cartridge. The robot will pick a cartridge from a storage rack which stores the multiple cartridges which are not currently in use. The robot will then insert the cartridge into a loader of the selected tape drive. When the system no longer needs to access the tape cartridge, the robot will grip the cartridge when the loader has unloaded the cartridge and return it to the storage rack.
During a load operation, one type of robot will push forward until a hard stop is reached. A hard stop is indicated to the robot by the amount of current drawn on the motor of the robot which turns a lead screw which advances the cartridge gripper. Until a hard stop is reached by the robot, the robot will continue to push the tape cartridge forward.
For other types of robots, the robot will push forward until it has reached a particular predetermined location.
Some tape drive systems include a movable tray within the loader of the drive. The tray moves freely when a loader motor is not operating. When a tape cartridge is inserted into this type of tape drive, the tray begins to receive the cartridge. At a predetermined point, a forward insertion movement should be stopped. At this point, the tray is then moved by the loader motor in order to complete the loading process. This type of tape drive does not provide a hard stop.
Providing a hard stop in a tape drive system is beneficial when the drive is configured to be utilized with a robot. Robots expect to repeatedly place and pick tape cartridges from the same physical location. Providing a hard stop simplifies the pick and place operation and improves the reliability if the tape cartridge is always located in the same place. The hard stop thus lets the robot place the cartridge into a non-moving location and pick it up from the exact same non-moving location. This location is the tape drive's loader tray. Any motion of the loader tray during the pick and place operation contributes to failure of that operation.
Therefore a need exists for a method and system to provide a hard stop within a loader in a tape cartridge loading/unloading system having a moveable loader tray, where the tray moves freely when the loader motor is not operating.